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Potentiometer for U3V50AHV step up regulator


Hello. I have a U3V50AHV step up regulator which I want to use to drive a DC motor up to 14 V from a 3.7 LiIon battery.
I want to mount an external potentiometer instead of the onboard trimmer, I saw on the forum that the value is 100K or 50K.
My problem is that I want to limit the maximum output to 15 V and use the entire range of the potentiometer. How can I do this? Can I solve the problem only with the potentiometer or do I need an external voltage divider?



PS: a second question concerns the input voltage: I have two choices: to use a 3.7 V battery or the 5V output of another step-up (typical USB charger circuit). Would it be a problem to use the 5V stepped up voltage? Should I stick better with the “real” 3.7 V?



Sorry, that level of modification is beyond what we can help you with. If your main point is to be able to set the voltage more precisely, you can try replacing the 100k pot with a multi-turn pot that you can set more carefully. You should keep the wires as short as possible, make sure they don’t short to anything, and even then, the performance of the regulator could suffer.

Regarding cascading regulators, it’s probably going to be more efficient to just use one, but depending on the efficiencies of your two units at different operating points, cascading them could be more efficient. You could just try it both ways and see which is better in your application.



Thank you Nathan for your reply.

I will do as suggested.
You mentioned the fact that the regulator is very sensible for changes of the potentiometer, should I understand that its functionality in not intended to have the voltage regulated on a continuous basis? Please tell me if the regulator itself could cause some problems of driving a DC motor (small, low cost as the ones used for RC toys) on a continuous basis (1-2 hrs) and with continuous regulations of the speed (i.e. voltage)




A modification to the regulator like replacing the potentiometer with an external one might expose the feedback pin on the IC that controls the circuit to more noise, which might affect the stability of the regulator. The regulator should be able to run a small motor like the one you mentioned continuously as long as the current draw is within the output current specifications for the regulator.